diff --git a/src/librustc_typeck/check/expr.rs b/src/librustc_typeck/check/expr.rs new file mode 100644 index 000000000000..48c1c0b36ffb --- /dev/null +++ b/src/librustc_typeck/check/expr.rs @@ -0,0 +1,706 @@ +//! Type checking expressions. +//! +//! See `mod.rs` for more context on type checking in general. + +use crate::check::BreakableCtxt; +use crate::check::cast; +use crate::check::coercion::CoerceMany; +use crate::check::Diverges; +use crate::check::FnCtxt; +use crate::check::Expectation::{self, NoExpectation, ExpectHasType, ExpectCastableToType}; +use crate::check::fatally_break_rust; +use crate::check::report_unexpected_variant_res; +use crate::check::Needs; +use crate::middle::lang_items; +use crate::util::common::ErrorReported; + +use errors::Applicability; +use syntax::ast; +use syntax::symbol::sym; +use rustc::hir; +use rustc::hir::{ExprKind, QPath}; +use rustc::hir::def::{CtorKind, Res, DefKind}; +use rustc::infer; +use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; +use rustc::mir::interpret::GlobalId; +use rustc::ty; +use rustc::ty::adjustment::{ + Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, +}; +use rustc::ty::Ty; +use rustc::ty::TypeFoldable; +use rustc::ty::subst::InternalSubsts; +use rustc::traits::{self, ObligationCauseCode}; + +impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + pub(super) fn check_expr_kind( + &self, + expr: &'tcx hir::Expr, + expected: Expectation<'tcx>, + needs: Needs, + ) -> Ty<'tcx> { + debug!( + "check_expr_kind(expr={:?}, expected={:?}, needs={:?})", + expr, + expected, + needs, + ); + + let tcx = self.tcx; + let id = expr.hir_id; + match expr.node { + ExprKind::Box(ref subexpr) => { + let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| { + match ty.sty { + ty::Adt(def, _) if def.is_box() + => Expectation::rvalue_hint(self, ty.boxed_ty()), + _ => NoExpectation + } + }); + let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner); + tcx.mk_box(referent_ty) + } + + ExprKind::Lit(ref lit) => { + self.check_lit(&lit, expected) + } + ExprKind::Binary(op, ref lhs, ref rhs) => { + self.check_binop(expr, op, lhs, rhs) + } + ExprKind::AssignOp(op, ref lhs, ref rhs) => { + self.check_binop_assign(expr, op, lhs, rhs) + } + ExprKind::Unary(unop, ref oprnd) => { + let expected_inner = match unop { + hir::UnNot | hir::UnNeg => { + expected + } + hir::UnDeref => { + NoExpectation + } + }; + let needs = match unop { + hir::UnDeref => needs, + _ => Needs::None + }; + let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd, + expected_inner, + needs); + + if !oprnd_t.references_error() { + oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t); + match unop { + hir::UnDeref => { + if let Some(mt) = oprnd_t.builtin_deref(true) { + oprnd_t = mt.ty; + } else if let Some(ok) = self.try_overloaded_deref( + expr.span, oprnd_t, needs) { + let method = self.register_infer_ok_obligations(ok); + if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].sty { + let mutbl = match mutbl { + hir::MutImmutable => AutoBorrowMutability::Immutable, + hir::MutMutable => AutoBorrowMutability::Mutable { + // (It shouldn't actually matter for unary ops whether + // we enable two-phase borrows or not, since a unary + // op has no additional operands.) + allow_two_phase_borrow: AllowTwoPhase::No, + } + }; + self.apply_adjustments(oprnd, vec![Adjustment { + kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)), + target: method.sig.inputs()[0] + }]); + } + oprnd_t = self.make_overloaded_place_return_type(method).ty; + self.write_method_call(expr.hir_id, method); + } else { + let mut err = type_error_struct!( + tcx.sess, + expr.span, + oprnd_t, + E0614, + "type `{}` cannot be dereferenced", + oprnd_t, + ); + let sp = tcx.sess.source_map().start_point(expr.span); + if let Some(sp) = tcx.sess.parse_sess.ambiguous_block_expr_parse + .borrow().get(&sp) + { + tcx.sess.parse_sess.expr_parentheses_needed( + &mut err, + *sp, + None, + ); + } + err.emit(); + oprnd_t = tcx.types.err; + } + } + hir::UnNot => { + let result = self.check_user_unop(expr, oprnd_t, unop); + // If it's builtin, we can reuse the type, this helps inference. + if !(oprnd_t.is_integral() || oprnd_t.sty == ty::Bool) { + oprnd_t = result; + } + } + hir::UnNeg => { + let result = self.check_user_unop(expr, oprnd_t, unop); + // If it's builtin, we can reuse the type, this helps inference. + if !oprnd_t.is_numeric() { + oprnd_t = result; + } + } + } + } + oprnd_t + } + ExprKind::AddrOf(mutbl, ref oprnd) => { + let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| { + match ty.sty { + ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => { + if oprnd.is_place_expr() { + // Places may legitimately have unsized types. + // For example, dereferences of a fat pointer and + // the last field of a struct can be unsized. + ExpectHasType(ty) + } else { + Expectation::rvalue_hint(self, ty) + } + } + _ => NoExpectation + } + }); + let needs = Needs::maybe_mut_place(mutbl); + let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs); + + let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl }; + if tm.ty.references_error() { + tcx.types.err + } else { + // Note: at this point, we cannot say what the best lifetime + // is to use for resulting pointer. We want to use the + // shortest lifetime possible so as to avoid spurious borrowck + // errors. Moreover, the longest lifetime will depend on the + // precise details of the value whose address is being taken + // (and how long it is valid), which we don't know yet until type + // inference is complete. + // + // Therefore, here we simply generate a region variable. The + // region inferencer will then select the ultimate value. + // Finally, borrowck is charged with guaranteeing that the + // value whose address was taken can actually be made to live + // as long as it needs to live. + let region = self.next_region_var(infer::AddrOfRegion(expr.span)); + tcx.mk_ref(region, tm) + } + } + ExprKind::Path(ref qpath) => { + let (res, opt_ty, segs) = self.resolve_ty_and_res_ufcs(qpath, expr.hir_id, + expr.span); + let ty = match res { + Res::Err => { + self.set_tainted_by_errors(); + tcx.types.err + } + Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => { + report_unexpected_variant_res(tcx, res, expr.span, qpath); + tcx.types.err + } + _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, id).0, + }; + + if let ty::FnDef(..) = ty.sty { + let fn_sig = ty.fn_sig(tcx); + if !tcx.features().unsized_locals { + // We want to remove some Sized bounds from std functions, + // but don't want to expose the removal to stable Rust. + // i.e., we don't want to allow + // + // ```rust + // drop as fn(str); + // ``` + // + // to work in stable even if the Sized bound on `drop` is relaxed. + for i in 0..fn_sig.inputs().skip_binder().len() { + // We just want to check sizedness, so instead of introducing + // placeholder lifetimes with probing, we just replace higher lifetimes + // with fresh vars. + let input = self.replace_bound_vars_with_fresh_vars( + expr.span, + infer::LateBoundRegionConversionTime::FnCall, + &fn_sig.input(i)).0; + self.require_type_is_sized_deferred(input, expr.span, + traits::SizedArgumentType); + } + } + // Here we want to prevent struct constructors from returning unsized types. + // There were two cases this happened: fn pointer coercion in stable + // and usual function call in presense of unsized_locals. + // Also, as we just want to check sizedness, instead of introducing + // placeholder lifetimes with probing, we just replace higher lifetimes + // with fresh vars. + let output = self.replace_bound_vars_with_fresh_vars( + expr.span, + infer::LateBoundRegionConversionTime::FnCall, + &fn_sig.output()).0; + self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType); + } + + // We always require that the type provided as the value for + // a type parameter outlives the moment of instantiation. + let substs = self.tables.borrow().node_substs(expr.hir_id); + self.add_wf_bounds(substs, expr); + + ty + } + ExprKind::InlineAsm(_, ref outputs, ref inputs) => { + for expr in outputs.iter().chain(inputs.iter()) { + self.check_expr(expr); + } + tcx.mk_unit() + } + ExprKind::Break(destination, ref expr_opt) => { + if let Ok(target_id) = destination.target_id { + let (e_ty, cause); + if let Some(ref e) = *expr_opt { + // If this is a break with a value, we need to type-check + // the expression. Get an expected type from the loop context. + let opt_coerce_to = { + let mut enclosing_breakables = self.enclosing_breakables.borrow_mut(); + enclosing_breakables.find_breakable(target_id) + .coerce + .as_ref() + .map(|coerce| coerce.expected_ty()) + }; + + // If the loop context is not a `loop { }`, then break with + // a value is illegal, and `opt_coerce_to` will be `None`. + // Just set expectation to error in that case. + let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err); + + // Recurse without `enclosing_breakables` borrowed. + e_ty = self.check_expr_with_hint(e, coerce_to); + cause = self.misc(e.span); + } else { + // Otherwise, this is a break *without* a value. That's + // always legal, and is equivalent to `break ()`. + e_ty = tcx.mk_unit(); + cause = self.misc(expr.span); + } + + // Now that we have type-checked `expr_opt`, borrow + // the `enclosing_loops` field and let's coerce the + // type of `expr_opt` into what is expected. + let mut enclosing_breakables = self.enclosing_breakables.borrow_mut(); + let ctxt = enclosing_breakables.find_breakable(target_id); + if let Some(ref mut coerce) = ctxt.coerce { + if let Some(ref e) = *expr_opt { + coerce.coerce(self, &cause, e, e_ty); + } else { + assert!(e_ty.is_unit()); + coerce.coerce_forced_unit(self, &cause, &mut |_| (), true); + } + } else { + // If `ctxt.coerce` is `None`, we can just ignore + // the type of the expresison. This is because + // either this was a break *without* a value, in + // which case it is always a legal type (`()`), or + // else an error would have been flagged by the + // `loops` pass for using break with an expression + // where you are not supposed to. + assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0); + } + + ctxt.may_break = true; + + // the type of a `break` is always `!`, since it diverges + tcx.types.never + } else { + // Otherwise, we failed to find the enclosing loop; + // this can only happen if the `break` was not + // inside a loop at all, which is caught by the + // loop-checking pass. + if self.tcx.sess.err_count() == 0 { + self.tcx.sess.delay_span_bug(expr.span, + "break was outside loop, but no error was emitted"); + } + + // We still need to assign a type to the inner expression to + // prevent the ICE in #43162. + if let Some(ref e) = *expr_opt { + self.check_expr_with_hint(e, tcx.types.err); + + // ... except when we try to 'break rust;'. + // ICE this expression in particular (see #43162). + if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.node { + if path.segments.len() == 1 && + path.segments[0].ident.name == sym::rust { + fatally_break_rust(self.tcx.sess); + } + } + } + // There was an error; make type-check fail. + tcx.types.err + } + + } + ExprKind::Continue(destination) => { + if destination.target_id.is_ok() { + tcx.types.never + } else { + // There was an error; make type-check fail. + tcx.types.err + } + } + ExprKind::Ret(ref expr_opt) => { + if self.ret_coercion.is_none() { + struct_span_err!(self.tcx.sess, expr.span, E0572, + "return statement outside of function body").emit(); + } else if let Some(ref e) = *expr_opt { + if self.ret_coercion_span.borrow().is_none() { + *self.ret_coercion_span.borrow_mut() = Some(e.span); + } + self.check_return_expr(e); + } else { + let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut(); + if self.ret_coercion_span.borrow().is_none() { + *self.ret_coercion_span.borrow_mut() = Some(expr.span); + } + let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression); + if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) { + coercion.coerce_forced_unit( + self, + &cause, + &mut |db| { + db.span_label( + fn_decl.output.span(), + format!( + "expected `{}` because of this return type", + fn_decl.output, + ), + ); + }, + true, + ); + } else { + coercion.coerce_forced_unit(self, &cause, &mut |_| (), true); + } + } + tcx.types.never + } + ExprKind::Assign(ref lhs, ref rhs) => { + self.check_assign(expr, expected, lhs, rhs) + } + ExprKind::While(ref cond, ref body, _) => { + let ctxt = BreakableCtxt { + // cannot use break with a value from a while loop + coerce: None, + may_break: false, // Will get updated if/when we find a `break`. + }; + + let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || { + self.check_expr_has_type_or_error(&cond, tcx.types.bool); + let cond_diverging = self.diverges.get(); + self.check_block_no_value(&body); + + // We may never reach the body so it diverging means nothing. + self.diverges.set(cond_diverging); + }); + + if ctxt.may_break { + // No way to know whether it's diverging because + // of a `break` or an outer `break` or `return`. + self.diverges.set(Diverges::Maybe); + } + + self.tcx.mk_unit() + } + ExprKind::Loop(ref body, _, source) => { + let coerce = match source { + // you can only use break with a value from a normal `loop { }` + hir::LoopSource::Loop => { + let coerce_to = expected.coercion_target_type(self, body.span); + Some(CoerceMany::new(coerce_to)) + } + + hir::LoopSource::WhileLet | + hir::LoopSource::ForLoop => { + None + } + }; + + let ctxt = BreakableCtxt { + coerce, + may_break: false, // Will get updated if/when we find a `break`. + }; + + let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || { + self.check_block_no_value(&body); + }); + + if ctxt.may_break { + // No way to know whether it's diverging because + // of a `break` or an outer `break` or `return`. + self.diverges.set(Diverges::Maybe); + } + + // If we permit break with a value, then result type is + // the LUB of the breaks (possibly ! if none); else, it + // is nil. This makes sense because infinite loops + // (which would have type !) are only possible iff we + // permit break with a value [1]. + if ctxt.coerce.is_none() && !ctxt.may_break { + // [1] + self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break"); + } + ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit()) + } + ExprKind::Match(ref discrim, ref arms, match_src) => { + self.check_match(expr, &discrim, arms, expected, match_src) + } + ExprKind::Closure(capture, ref decl, body_id, _, gen) => { + self.check_expr_closure(expr, capture, &decl, body_id, gen, expected) + } + ExprKind::Block(ref body, _) => { + self.check_block_with_expected(&body, expected) + } + ExprKind::Call(ref callee, ref args) => { + self.check_call(expr, &callee, args, expected) + } + ExprKind::MethodCall(ref segment, span, ref args) => { + self.check_method_call(expr, segment, span, args, expected, needs) + } + ExprKind::Cast(ref e, ref t) => { + // Find the type of `e`. Supply hints based on the type we are casting to, + // if appropriate. + let t_cast = self.to_ty_saving_user_provided_ty(t); + let t_cast = self.resolve_vars_if_possible(&t_cast); + let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast)); + let t_cast = self.resolve_vars_if_possible(&t_cast); + + // Eagerly check for some obvious errors. + if t_expr.references_error() || t_cast.references_error() { + tcx.types.err + } else { + // Defer other checks until we're done type checking. + let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut(); + match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) { + Ok(cast_check) => { + deferred_cast_checks.push(cast_check); + t_cast + } + Err(ErrorReported) => { + tcx.types.err + } + } + } + } + ExprKind::Type(ref e, ref t) => { + let ty = self.to_ty_saving_user_provided_ty(&t); + self.check_expr_eq_type(&e, ty); + ty + } + ExprKind::DropTemps(ref e) => { + self.check_expr_with_expectation(e, expected) + } + ExprKind::Array(ref args) => { + let uty = expected.to_option(self).and_then(|uty| { + match uty.sty { + ty::Array(ty, _) | ty::Slice(ty) => Some(ty), + _ => None + } + }); + + let element_ty = if !args.is_empty() { + let coerce_to = uty.unwrap_or_else(|| { + self.next_ty_var(TypeVariableOrigin { + kind: TypeVariableOriginKind::TypeInference, + span: expr.span, + }) + }); + let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args); + assert_eq!(self.diverges.get(), Diverges::Maybe); + for e in args { + let e_ty = self.check_expr_with_hint(e, coerce_to); + let cause = self.misc(e.span); + coerce.coerce(self, &cause, e, e_ty); + } + coerce.complete(self) + } else { + self.next_ty_var(TypeVariableOrigin { + kind: TypeVariableOriginKind::TypeInference, + span: expr.span, + }) + }; + tcx.mk_array(element_ty, args.len() as u64) + } + ExprKind::Repeat(ref element, ref count) => { + let count_def_id = tcx.hir().local_def_id_from_hir_id(count.hir_id); + let count = if self.const_param_def_id(count).is_some() { + Ok(self.to_const(count, self.tcx.type_of(count_def_id))) + } else { + let param_env = ty::ParamEnv::empty(); + let substs = InternalSubsts::identity_for_item(tcx.global_tcx(), count_def_id); + let instance = ty::Instance::resolve( + tcx.global_tcx(), + param_env, + count_def_id, + substs, + ).unwrap(); + let global_id = GlobalId { + instance, + promoted: None + }; + + tcx.const_eval(param_env.and(global_id)) + }; + + let uty = match expected { + ExpectHasType(uty) => { + match uty.sty { + ty::Array(ty, _) | ty::Slice(ty) => Some(ty), + _ => None + } + } + _ => None + }; + + let (element_ty, t) = match uty { + Some(uty) => { + self.check_expr_coercable_to_type(&element, uty); + (uty, uty) + } + None => { + let ty = self.next_ty_var(TypeVariableOrigin { + kind: TypeVariableOriginKind::MiscVariable, + span: element.span, + }); + let element_ty = self.check_expr_has_type_or_error(&element, ty); + (element_ty, ty) + } + }; + + if let Ok(count) = count { + let zero_or_one = count.assert_usize(tcx).map_or(false, |count| count <= 1); + if !zero_or_one { + // For [foo, ..n] where n > 1, `foo` must have + // Copy type: + let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem); + self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item); + } + } + + if element_ty.references_error() { + tcx.types.err + } else if let Ok(count) = count { + tcx.mk_ty(ty::Array(t, count)) + } else { + tcx.types.err + } + } + ExprKind::Tup(ref elts) => { + let flds = expected.only_has_type(self).and_then(|ty| { + let ty = self.resolve_type_vars_with_obligations(ty); + match ty.sty { + ty::Tuple(ref flds) => Some(&flds[..]), + _ => None + } + }); + + let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| { + let t = match flds { + Some(ref fs) if i < fs.len() => { + let ety = fs[i].expect_ty(); + self.check_expr_coercable_to_type(&e, ety); + ety + } + _ => { + self.check_expr_with_expectation(&e, NoExpectation) + } + }; + t + }); + let tuple = tcx.mk_tup(elt_ts_iter); + if tuple.references_error() { + tcx.types.err + } else { + self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized); + tuple + } + } + ExprKind::Struct(ref qpath, ref fields, ref base_expr) => { + self.check_expr_struct(expr, expected, qpath, fields, base_expr) + } + ExprKind::Field(ref base, field) => { + self.check_field(expr, needs, &base, field) + } + ExprKind::Index(ref base, ref idx) => { + let base_t = self.check_expr_with_needs(&base, needs); + let idx_t = self.check_expr(&idx); + + if base_t.references_error() { + base_t + } else if idx_t.references_error() { + idx_t + } else { + let base_t = self.structurally_resolved_type(base.span, base_t); + match self.lookup_indexing(expr, base, base_t, idx_t, needs) { + Some((index_ty, element_ty)) => { + // two-phase not needed because index_ty is never mutable + self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No); + element_ty + } + None => { + let mut err = + type_error_struct!(tcx.sess, expr.span, base_t, E0608, + "cannot index into a value of type `{}`", + base_t); + // Try to give some advice about indexing tuples. + if let ty::Tuple(..) = base_t.sty { + let mut needs_note = true; + // If the index is an integer, we can show the actual + // fixed expression: + if let ExprKind::Lit(ref lit) = idx.node { + if let ast::LitKind::Int(i, + ast::LitIntType::Unsuffixed) = lit.node { + let snip = tcx.sess.source_map().span_to_snippet(base.span); + if let Ok(snip) = snip { + err.span_suggestion( + expr.span, + "to access tuple elements, use", + format!("{}.{}", snip, i), + Applicability::MachineApplicable, + ); + needs_note = false; + } + } + } + if needs_note { + err.help("to access tuple elements, use tuple indexing \ + syntax (e.g., `tuple.0`)"); + } + } + err.emit(); + self.tcx.types.err + } + } + } + } + ExprKind::Yield(ref value) => { + match self.yield_ty { + Some(ty) => { + self.check_expr_coercable_to_type(&value, ty); + } + None => { + struct_span_err!(self.tcx.sess, expr.span, E0627, + "yield statement outside of generator literal").emit(); + } + } + tcx.mk_unit() + } + hir::ExprKind::Err => { + tcx.types.err + } + } + } +} diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs index c857eac5d3c1..1cb064c23a96 100644 --- a/src/librustc_typeck/check/mod.rs +++ b/src/librustc_typeck/check/mod.rs @@ -74,6 +74,7 @@ pub mod writeback; mod regionck; pub mod coercion; pub mod demand; +mod expr; pub mod method; mod upvar; mod wfcheck; @@ -88,7 +89,7 @@ mod op; use crate::astconv::{AstConv, PathSeg}; use errors::{Applicability, DiagnosticBuilder, DiagnosticId}; use rustc::hir::{self, ExprKind, GenericArg, ItemKind, Node, PatKind, QPath}; -use rustc::hir::def::{CtorOf, CtorKind, Res, DefKind}; +use rustc::hir::def::{CtorOf, Res, DefKind}; use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE}; use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap}; use rustc::hir::itemlikevisit::ItemLikeVisitor; @@ -3923,7 +3924,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { adt_ty } - /// Invariant: /// If an expression has any sub-expressions that result in a type error, /// inspecting that expression's type with `ty.references_error()` will return @@ -3983,677 +3983,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { ty } - fn check_expr_kind( - &self, - expr: &'tcx hir::Expr, - expected: Expectation<'tcx>, - needs: Needs, - ) -> Ty<'tcx> { - debug!( - "check_expr_kind(expr={:?}, expected={:?}, needs={:?})", - expr, - expected, - needs, - ); - - let tcx = self.tcx; - let id = expr.hir_id; - match expr.node { - ExprKind::Box(ref subexpr) => { - let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| { - match ty.sty { - ty::Adt(def, _) if def.is_box() - => Expectation::rvalue_hint(self, ty.boxed_ty()), - _ => NoExpectation - } - }); - let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner); - tcx.mk_box(referent_ty) - } - - ExprKind::Lit(ref lit) => { - self.check_lit(&lit, expected) - } - ExprKind::Binary(op, ref lhs, ref rhs) => { - self.check_binop(expr, op, lhs, rhs) - } - ExprKind::AssignOp(op, ref lhs, ref rhs) => { - self.check_binop_assign(expr, op, lhs, rhs) - } - ExprKind::Unary(unop, ref oprnd) => { - let expected_inner = match unop { - hir::UnNot | hir::UnNeg => { - expected - } - hir::UnDeref => { - NoExpectation - } - }; - let needs = match unop { - hir::UnDeref => needs, - _ => Needs::None - }; - let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd, - expected_inner, - needs); - - if !oprnd_t.references_error() { - oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t); - match unop { - hir::UnDeref => { - if let Some(mt) = oprnd_t.builtin_deref(true) { - oprnd_t = mt.ty; - } else if let Some(ok) = self.try_overloaded_deref( - expr.span, oprnd_t, needs) { - let method = self.register_infer_ok_obligations(ok); - if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].sty { - let mutbl = match mutbl { - hir::MutImmutable => AutoBorrowMutability::Immutable, - hir::MutMutable => AutoBorrowMutability::Mutable { - // (It shouldn't actually matter for unary ops whether - // we enable two-phase borrows or not, since a unary - // op has no additional operands.) - allow_two_phase_borrow: AllowTwoPhase::No, - } - }; - self.apply_adjustments(oprnd, vec![Adjustment { - kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)), - target: method.sig.inputs()[0] - }]); - } - oprnd_t = self.make_overloaded_place_return_type(method).ty; - self.write_method_call(expr.hir_id, method); - } else { - let mut err = type_error_struct!( - tcx.sess, - expr.span, - oprnd_t, - E0614, - "type `{}` cannot be dereferenced", - oprnd_t, - ); - let sp = tcx.sess.source_map().start_point(expr.span); - if let Some(sp) = tcx.sess.parse_sess.ambiguous_block_expr_parse - .borrow().get(&sp) - { - tcx.sess.parse_sess.expr_parentheses_needed( - &mut err, - *sp, - None, - ); - } - err.emit(); - oprnd_t = tcx.types.err; - } - } - hir::UnNot => { - let result = self.check_user_unop(expr, oprnd_t, unop); - // If it's builtin, we can reuse the type, this helps inference. - if !(oprnd_t.is_integral() || oprnd_t.sty == ty::Bool) { - oprnd_t = result; - } - } - hir::UnNeg => { - let result = self.check_user_unop(expr, oprnd_t, unop); - // If it's builtin, we can reuse the type, this helps inference. - if !oprnd_t.is_numeric() { - oprnd_t = result; - } - } - } - } - oprnd_t - } - ExprKind::AddrOf(mutbl, ref oprnd) => { - let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| { - match ty.sty { - ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => { - if oprnd.is_place_expr() { - // Places may legitimately have unsized types. - // For example, dereferences of a fat pointer and - // the last field of a struct can be unsized. - ExpectHasType(ty) - } else { - Expectation::rvalue_hint(self, ty) - } - } - _ => NoExpectation - } - }); - let needs = Needs::maybe_mut_place(mutbl); - let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs); - - let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl }; - if tm.ty.references_error() { - tcx.types.err - } else { - // Note: at this point, we cannot say what the best lifetime - // is to use for resulting pointer. We want to use the - // shortest lifetime possible so as to avoid spurious borrowck - // errors. Moreover, the longest lifetime will depend on the - // precise details of the value whose address is being taken - // (and how long it is valid), which we don't know yet until type - // inference is complete. - // - // Therefore, here we simply generate a region variable. The - // region inferencer will then select the ultimate value. - // Finally, borrowck is charged with guaranteeing that the - // value whose address was taken can actually be made to live - // as long as it needs to live. - let region = self.next_region_var(infer::AddrOfRegion(expr.span)); - tcx.mk_ref(region, tm) - } - } - ExprKind::Path(ref qpath) => { - let (res, opt_ty, segs) = self.resolve_ty_and_res_ufcs(qpath, expr.hir_id, - expr.span); - let ty = match res { - Res::Err => { - self.set_tainted_by_errors(); - tcx.types.err - } - Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => { - report_unexpected_variant_res(tcx, res, expr.span, qpath); - tcx.types.err - } - _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, id).0, - }; - - if let ty::FnDef(..) = ty.sty { - let fn_sig = ty.fn_sig(tcx); - if !tcx.features().unsized_locals { - // We want to remove some Sized bounds from std functions, - // but don't want to expose the removal to stable Rust. - // i.e., we don't want to allow - // - // ```rust - // drop as fn(str); - // ``` - // - // to work in stable even if the Sized bound on `drop` is relaxed. - for i in 0..fn_sig.inputs().skip_binder().len() { - // We just want to check sizedness, so instead of introducing - // placeholder lifetimes with probing, we just replace higher lifetimes - // with fresh vars. - let input = self.replace_bound_vars_with_fresh_vars( - expr.span, - infer::LateBoundRegionConversionTime::FnCall, - &fn_sig.input(i)).0; - self.require_type_is_sized_deferred(input, expr.span, - traits::SizedArgumentType); - } - } - // Here we want to prevent struct constructors from returning unsized types. - // There were two cases this happened: fn pointer coercion in stable - // and usual function call in presense of unsized_locals. - // Also, as we just want to check sizedness, instead of introducing - // placeholder lifetimes with probing, we just replace higher lifetimes - // with fresh vars. - let output = self.replace_bound_vars_with_fresh_vars( - expr.span, - infer::LateBoundRegionConversionTime::FnCall, - &fn_sig.output()).0; - self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType); - } - - // We always require that the type provided as the value for - // a type parameter outlives the moment of instantiation. - let substs = self.tables.borrow().node_substs(expr.hir_id); - self.add_wf_bounds(substs, expr); - - ty - } - ExprKind::InlineAsm(_, ref outputs, ref inputs) => { - for expr in outputs.iter().chain(inputs.iter()) { - self.check_expr(expr); - } - tcx.mk_unit() - } - ExprKind::Break(destination, ref expr_opt) => { - if let Ok(target_id) = destination.target_id { - let (e_ty, cause); - if let Some(ref e) = *expr_opt { - // If this is a break with a value, we need to type-check - // the expression. Get an expected type from the loop context. - let opt_coerce_to = { - let mut enclosing_breakables = self.enclosing_breakables.borrow_mut(); - enclosing_breakables.find_breakable(target_id) - .coerce - .as_ref() - .map(|coerce| coerce.expected_ty()) - }; - - // If the loop context is not a `loop { }`, then break with - // a value is illegal, and `opt_coerce_to` will be `None`. - // Just set expectation to error in that case. - let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err); - - // Recurse without `enclosing_breakables` borrowed. - e_ty = self.check_expr_with_hint(e, coerce_to); - cause = self.misc(e.span); - } else { - // Otherwise, this is a break *without* a value. That's - // always legal, and is equivalent to `break ()`. - e_ty = tcx.mk_unit(); - cause = self.misc(expr.span); - } - - // Now that we have type-checked `expr_opt`, borrow - // the `enclosing_loops` field and let's coerce the - // type of `expr_opt` into what is expected. - let mut enclosing_breakables = self.enclosing_breakables.borrow_mut(); - let ctxt = enclosing_breakables.find_breakable(target_id); - if let Some(ref mut coerce) = ctxt.coerce { - if let Some(ref e) = *expr_opt { - coerce.coerce(self, &cause, e, e_ty); - } else { - assert!(e_ty.is_unit()); - coerce.coerce_forced_unit(self, &cause, &mut |_| (), true); - } - } else { - // If `ctxt.coerce` is `None`, we can just ignore - // the type of the expresison. This is because - // either this was a break *without* a value, in - // which case it is always a legal type (`()`), or - // else an error would have been flagged by the - // `loops` pass for using break with an expression - // where you are not supposed to. - assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0); - } - - ctxt.may_break = true; - - // the type of a `break` is always `!`, since it diverges - tcx.types.never - } else { - // Otherwise, we failed to find the enclosing loop; - // this can only happen if the `break` was not - // inside a loop at all, which is caught by the - // loop-checking pass. - if self.tcx.sess.err_count() == 0 { - self.tcx.sess.delay_span_bug(expr.span, - "break was outside loop, but no error was emitted"); - } - - // We still need to assign a type to the inner expression to - // prevent the ICE in #43162. - if let Some(ref e) = *expr_opt { - self.check_expr_with_hint(e, tcx.types.err); - - // ... except when we try to 'break rust;'. - // ICE this expression in particular (see #43162). - if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.node { - if path.segments.len() == 1 && - path.segments[0].ident.name == sym::rust { - fatally_break_rust(self.tcx.sess); - } - } - } - // There was an error; make type-check fail. - tcx.types.err - } - - } - ExprKind::Continue(destination) => { - if destination.target_id.is_ok() { - tcx.types.never - } else { - // There was an error; make type-check fail. - tcx.types.err - } - } - ExprKind::Ret(ref expr_opt) => { - if self.ret_coercion.is_none() { - struct_span_err!(self.tcx.sess, expr.span, E0572, - "return statement outside of function body").emit(); - } else if let Some(ref e) = *expr_opt { - if self.ret_coercion_span.borrow().is_none() { - *self.ret_coercion_span.borrow_mut() = Some(e.span); - } - self.check_return_expr(e); - } else { - let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut(); - if self.ret_coercion_span.borrow().is_none() { - *self.ret_coercion_span.borrow_mut() = Some(expr.span); - } - let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression); - if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) { - coercion.coerce_forced_unit( - self, - &cause, - &mut |db| { - db.span_label( - fn_decl.output.span(), - format!( - "expected `{}` because of this return type", - fn_decl.output, - ), - ); - }, - true, - ); - } else { - coercion.coerce_forced_unit(self, &cause, &mut |_| (), true); - } - } - tcx.types.never - } - ExprKind::Assign(ref lhs, ref rhs) => { - self.check_assign(expr, expected, lhs, rhs) - } - ExprKind::While(ref cond, ref body, _) => { - let ctxt = BreakableCtxt { - // cannot use break with a value from a while loop - coerce: None, - may_break: false, // Will get updated if/when we find a `break`. - }; - - let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || { - self.check_expr_has_type_or_error(&cond, tcx.types.bool); - let cond_diverging = self.diverges.get(); - self.check_block_no_value(&body); - - // We may never reach the body so it diverging means nothing. - self.diverges.set(cond_diverging); - }); - - if ctxt.may_break { - // No way to know whether it's diverging because - // of a `break` or an outer `break` or `return`. - self.diverges.set(Diverges::Maybe); - } - - self.tcx.mk_unit() - } - ExprKind::Loop(ref body, _, source) => { - let coerce = match source { - // you can only use break with a value from a normal `loop { }` - hir::LoopSource::Loop => { - let coerce_to = expected.coercion_target_type(self, body.span); - Some(CoerceMany::new(coerce_to)) - } - - hir::LoopSource::WhileLet | - hir::LoopSource::ForLoop => { - None - } - }; - - let ctxt = BreakableCtxt { - coerce, - may_break: false, // Will get updated if/when we find a `break`. - }; - - let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || { - self.check_block_no_value(&body); - }); - - if ctxt.may_break { - // No way to know whether it's diverging because - // of a `break` or an outer `break` or `return`. - self.diverges.set(Diverges::Maybe); - } - - // If we permit break with a value, then result type is - // the LUB of the breaks (possibly ! if none); else, it - // is nil. This makes sense because infinite loops - // (which would have type !) are only possible iff we - // permit break with a value [1]. - if ctxt.coerce.is_none() && !ctxt.may_break { - // [1] - self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break"); - } - ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit()) - } - ExprKind::Match(ref discrim, ref arms, match_src) => { - self.check_match(expr, &discrim, arms, expected, match_src) - } - ExprKind::Closure(capture, ref decl, body_id, _, gen) => { - self.check_expr_closure(expr, capture, &decl, body_id, gen, expected) - } - ExprKind::Block(ref body, _) => { - self.check_block_with_expected(&body, expected) - } - ExprKind::Call(ref callee, ref args) => { - self.check_call(expr, &callee, args, expected) - } - ExprKind::MethodCall(ref segment, span, ref args) => { - self.check_method_call(expr, segment, span, args, expected, needs) - } - ExprKind::Cast(ref e, ref t) => { - // Find the type of `e`. Supply hints based on the type we are casting to, - // if appropriate. - let t_cast = self.to_ty_saving_user_provided_ty(t); - let t_cast = self.resolve_vars_if_possible(&t_cast); - let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast)); - let t_cast = self.resolve_vars_if_possible(&t_cast); - - // Eagerly check for some obvious errors. - if t_expr.references_error() || t_cast.references_error() { - tcx.types.err - } else { - // Defer other checks until we're done type checking. - let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut(); - match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) { - Ok(cast_check) => { - deferred_cast_checks.push(cast_check); - t_cast - } - Err(ErrorReported) => { - tcx.types.err - } - } - } - } - ExprKind::Type(ref e, ref t) => { - let ty = self.to_ty_saving_user_provided_ty(&t); - self.check_expr_eq_type(&e, ty); - ty - } - ExprKind::DropTemps(ref e) => { - self.check_expr_with_expectation(e, expected) - } - ExprKind::Array(ref args) => { - let uty = expected.to_option(self).and_then(|uty| { - match uty.sty { - ty::Array(ty, _) | ty::Slice(ty) => Some(ty), - _ => None - } - }); - - let element_ty = if !args.is_empty() { - let coerce_to = uty.unwrap_or_else(|| { - self.next_ty_var(TypeVariableOrigin { - kind: TypeVariableOriginKind::TypeInference, - span: expr.span, - }) - }); - let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args); - assert_eq!(self.diverges.get(), Diverges::Maybe); - for e in args { - let e_ty = self.check_expr_with_hint(e, coerce_to); - let cause = self.misc(e.span); - coerce.coerce(self, &cause, e, e_ty); - } - coerce.complete(self) - } else { - self.next_ty_var(TypeVariableOrigin { - kind: TypeVariableOriginKind::TypeInference, - span: expr.span, - }) - }; - tcx.mk_array(element_ty, args.len() as u64) - } - ExprKind::Repeat(ref element, ref count) => { - let count_def_id = tcx.hir().local_def_id_from_hir_id(count.hir_id); - let count = if self.const_param_def_id(count).is_some() { - Ok(self.to_const(count, self.tcx.type_of(count_def_id))) - } else { - let param_env = ty::ParamEnv::empty(); - let substs = InternalSubsts::identity_for_item(tcx.global_tcx(), count_def_id); - let instance = ty::Instance::resolve( - tcx.global_tcx(), - param_env, - count_def_id, - substs, - ).unwrap(); - let global_id = GlobalId { - instance, - promoted: None - }; - - tcx.const_eval(param_env.and(global_id)) - }; - - let uty = match expected { - ExpectHasType(uty) => { - match uty.sty { - ty::Array(ty, _) | ty::Slice(ty) => Some(ty), - _ => None - } - } - _ => None - }; - - let (element_ty, t) = match uty { - Some(uty) => { - self.check_expr_coercable_to_type(&element, uty); - (uty, uty) - } - None => { - let ty = self.next_ty_var(TypeVariableOrigin { - kind: TypeVariableOriginKind::MiscVariable, - span: element.span, - }); - let element_ty = self.check_expr_has_type_or_error(&element, ty); - (element_ty, ty) - } - }; - - if let Ok(count) = count { - let zero_or_one = count.assert_usize(tcx).map_or(false, |count| count <= 1); - if !zero_or_one { - // For [foo, ..n] where n > 1, `foo` must have - // Copy type: - let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem); - self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item); - } - } - - if element_ty.references_error() { - tcx.types.err - } else if let Ok(count) = count { - tcx.mk_ty(ty::Array(t, count)) - } else { - tcx.types.err - } - } - ExprKind::Tup(ref elts) => { - let flds = expected.only_has_type(self).and_then(|ty| { - let ty = self.resolve_type_vars_with_obligations(ty); - match ty.sty { - ty::Tuple(ref flds) => Some(&flds[..]), - _ => None - } - }); - - let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| { - let t = match flds { - Some(ref fs) if i < fs.len() => { - let ety = fs[i].expect_ty(); - self.check_expr_coercable_to_type(&e, ety); - ety - } - _ => { - self.check_expr_with_expectation(&e, NoExpectation) - } - }; - t - }); - let tuple = tcx.mk_tup(elt_ts_iter); - if tuple.references_error() { - tcx.types.err - } else { - self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized); - tuple - } - } - ExprKind::Struct(ref qpath, ref fields, ref base_expr) => { - self.check_expr_struct(expr, expected, qpath, fields, base_expr) - } - ExprKind::Field(ref base, field) => { - self.check_field(expr, needs, &base, field) - } - ExprKind::Index(ref base, ref idx) => { - let base_t = self.check_expr_with_needs(&base, needs); - let idx_t = self.check_expr(&idx); - - if base_t.references_error() { - base_t - } else if idx_t.references_error() { - idx_t - } else { - let base_t = self.structurally_resolved_type(base.span, base_t); - match self.lookup_indexing(expr, base, base_t, idx_t, needs) { - Some((index_ty, element_ty)) => { - // two-phase not needed because index_ty is never mutable - self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No); - element_ty - } - None => { - let mut err = - type_error_struct!(tcx.sess, expr.span, base_t, E0608, - "cannot index into a value of type `{}`", - base_t); - // Try to give some advice about indexing tuples. - if let ty::Tuple(..) = base_t.sty { - let mut needs_note = true; - // If the index is an integer, we can show the actual - // fixed expression: - if let ExprKind::Lit(ref lit) = idx.node { - if let ast::LitKind::Int(i, - ast::LitIntType::Unsuffixed) = lit.node { - let snip = tcx.sess.source_map().span_to_snippet(base.span); - if let Ok(snip) = snip { - err.span_suggestion( - expr.span, - "to access tuple elements, use", - format!("{}.{}", snip, i), - Applicability::MachineApplicable, - ); - needs_note = false; - } - } - } - if needs_note { - err.help("to access tuple elements, use tuple indexing \ - syntax (e.g., `tuple.0`)"); - } - } - err.emit(); - self.tcx.types.err - } - } - } - } - ExprKind::Yield(ref value) => { - match self.yield_ty { - Some(ty) => { - self.check_expr_coercable_to_type(&value, ty); - } - None => { - struct_span_err!(self.tcx.sess, expr.span, E0627, - "yield statement outside of generator literal").emit(); - } - } - tcx.mk_unit() - } - hir::ExprKind::Err => { - tcx.types.err - } - } - } - /// Type check assignment expression `expr` of form `lhs = rhs`. /// The expected type is `()` and is passsed to the function for the purposes of diagnostics. fn check_assign(